The present invention concerns ablation catheters and systems useful for the treatment of cardiac arrhythmias, and particularly atrial arhythmias.
Atrial fibrillation is one of the most common cardiac arrhythmia. Health consequences associated with atrial fibrillation include decreased cardiac output, less regular ventricular rhythm, the formation of blood clots in the atrial appendages, and an increased incidence of stroke. While some drugs are available for the treatment of atrial fibrillation, they have a number of side effects which reduce their therapeutic utility.
Atrial fibrillation may be treated by the xe2x80x9cmaze procedurexe2x80x9d. The maze procedure is a surgical technique that involves the formation of a pattern of incisions in the left and/or right atrial walls. This procedure is intensely invasive with a difficult recovery, and it has accordingly been desirable to establish less invasive, closed-heart, catheter based techniques for treating atrial fibrillation.
Swartz et al., U.S. Pat. No. 5,690,611, describes a process for the treatment of atrial arrhythmia in which a catheter is introduced into the left or right atrium through a guiding introducer and a pattern of ablation tracks formed therein. A problem with this technique is that an extensive number of lengthy ablation tracks are formed, and since linear lines are formed by slowly dragging the catheter procedure time is extensive.
Avitall, U.S. Pat. No. 5,687,723, describes a mapping and ablation catheter for treating atrial fibrillation. The device is designed to produce linear lesions from an array of mapping and ablation electrodes serially positioned along the catheter. A vascular guide wire is included fixed to the distal tip of the catheter to help navigate the device. The hook-shaped vascular guide wire may be inserted into a pulmonary vein and anchored therein, apparently by a hooking action, to help adjust the electrode-carrying segment of the catheter (FIGS. 14-15; column 9). However, Avitall still necessitates elongate linear lesions in the manner described by Swartz et al.
H. Calkins et al., Am. J. Cardiol. 83, 227D-236D (1999), describes a system that incorporates multiple preshaped steerable catheters. The pre-shaped steerable catheters are formed by embedding a preshaped Nitinol stylet in the shaft thereof. The catheters can deliver a variety of lesion shapes, from localized spot lesions to lesions that are 8 centimeters in length.
Recent studies have suggested that focal arrhythmia can originate from a tissue region along the pulmonary veins extending from the left atrium, particularly the superior pulmonary veins. For example, Lesh et al., U.S. Pat. No. 6,012,457, provide a device that forms a circumferential lesion and circumferential conduction block in a pulmonary vein. The device is a balloon that carries a circumferential electrode, and extends over a guidewire through the atrium and into, or partially into, a vein. The balloon centers and secures the device in the vein, where the electrode ablates a circumferential region of tissue within the vein, or within the vein and extending out into the atrium. While this device reduces the amount of tissue that must be ablated to a smaller circumferential pattern, a problem with this approach is that the ablation of tissue within the vein can lead to pulmonary vein stenosis, which may induce pulmonary hypertension. See, e.g., I. Robbins et al., Circulation 98, 1769 (1988); G. Taylor et al., Pace 22 (Part II), 712 (1999).
Accordingly, an object of this invention is to provide a closed-heartprocedure for treating atrial arrhythmia in which the region of tissue ablation is reduced, yet the ablation of tissue within a pulmonary vein is avoided.
A first aspect of the present invention is a cardiac ablation catheter apparatus for producing a circumferential ablation that electrically isolates an inner wall portion (e.g., an atrial wall portion) of a heart from a connecting vessel or orifice therein (e.g., a pulmonary vein extending into an atrial wall portion). The apparatus comprises:
(a) an elongate centering catheter having a distal end portion;
(b) an expandable centering element connected to the centering catheter distal end portion and configured for positioning within the vessel (e.g., the pulmonary vein) when in a retracted configuration, and for securing the elongate centering catheter in a substantially axially aligned position with respect to the vessel when the centering is in an expanded configuration;
(c) an ablation catheter slidably connected to the centering catheter the ablation element having a distal end portion, and
(d) an expandable ablation element connected to the ablation catheter distal end portion, the ablation element configured to form a circumferential ablation on the wall portion around the elongate centering catheter when the centering catheter is axially aligned with respect to the vessel.
The expandable centering element may be any suitable device, including a balloon, an expandable cage or stent-like structure (referred to as a xe2x80x9cstentxe2x80x9d herein), a structure formed from a preformed stylet, etc. Likewise, the expandable ablation element may be any suitable device, including a balloon or stent, a structure formed from a preformed stylet, etc, with the ablation element carrying one or more ablation electrodes for ablating the target tissue. In another embodiment, the ablation element may comprise a plurality of expandable legs (e.g., at least three or four, up to eight, ten or more), with at least one of those expandable legs (optionally a plurality of those legs, and in one embodiment all of those legs) having an ablation electrode on a distal tip portion thereof. It will be appreciated that the ablation electrodes may be continuous or discontinuous around the vessel, with the circumferential ablation being formed by rotation of the ablation element when the electrodes are discontinuous.
In one embodiment of the invention, the centering catheter is slidably received on a guide wire, which guide wire serves to guide and place the centering catheter and then the ablation catheter into the appropriate heart chamber (e.g., the atrium). In another embodiment, the ablation catheter is itself a steerable catheter, incorporating a steering mechanism such as a preformed steering stylet operatively associated with a steering tendon.
A second aspect of the present invention is a cardiac ablation system for producing a circumferential ablation that electrically isolates a wall portion (e.g., an atrial wall portion) of a heart from a vessel such as a pulmonary vein extending into the wall portion, the system comprises a catheter as described above, with a power supply operably associated with the ablation element. Preferably, a first expansion actuator is operatively associated with the centering element, and a second expansion actuator operatively associated with the ablation element.
A third aspect of the present invention is a cardiac ablation method for producing a circumferential ablation that electrically isolates a wall portion such as an atrial wall portion of a heart from a vessel such as a pulmonary vein extending into the wall portion. The method comprises the steps of:
(a) inserting an elongate centering catheter having a distal end portion through an heart chamber such as an atrium into the vessel (e.g., a pulmonary vein), the distal end portion having an expandable centering element for engaging the vessel connected thereto;
(b) expanding the centering element in the vessel to secure the elongate centering catheter in a substantially axially aligned position with respect to the vessel; then
(c) inserting an ablation catheter slidably connected to the centering catheter into the chamber, the ablation catheter having an expandable ablation element connected to the distal end portion thereof; then
(d) positioning the ablation element on the chamber wall portion; and then
(e) forming a circumferential ablation around the elongate centering catheter on the wall portion in the chamber and outside of the vessel. Preferably, the inner diameter of the circumferential ablation is greater than the inner diameter of the vessel.
Because the apparatus described above provides an ablation element that can be slidably positioned along the centering catheter, rather than rigidly linking the two, and (in a preferred embodiment) further provides an ablation element whose diameter can be adjusted within the chamber after the ablation element is inserted into the chamber, but before forming the circumferential ablation, the apparatus disclosed herein simplifies the formation of the chamber wall ablation without undue intrusion of the ablation into a vessel such as a pulmonary vein.
In an alternative embodiment of the invention, the centering element can be a nonexpandable, compliant centering element (e.g., an elastic finger), the centering element typically having an outer diameter that is not greater than, and preferably smaller than, the inner diameter of the vessel into which it is inserted. Such a centering element obviates the need for an expansion mechanism associated with the centering element and advantageously makes the device mechanically simpler. When a nonexpandable, compliant centering element is employed, then the ablation element is configured with the diameter of the electrodes sufficiently wide so that the ablation formed thereby is on the wall of the chamber and does not intrude into the vessel into which the centering element is inserted, regardless of lateral position of the centering element in that vessel.
Accordingly, a fourth aspect of the present invention is a cardiac ablation apparatus for producing a circumferential ablation that electrically isolates a chamber wall portion of a heart from a vessel extending into the wall portion, the apparatus comprising:
(a) an elongate catheter having a distal end portion;
(b) a nonexpandable, compliant, centering element as described above connected to the catheter distal end portion and configured for positioning within the vessel; and
(c) an expandable ablation element connected to the catheter distal end portion, the ablation element configured to form a circumferential ablation on the wall portion around the centering element when the centering element is positioned in the vessel. The ablation element can be slidably connected to the catheter by providing a separate ablation catheter around a centering catheter as described above, or both the ablation element and the centering element can be permanently affixed (e.g., rigidly connected or integrally formed on) to the same catheter. The ablation element may be the same as any of those described above.
A fifth aspect of the present invention is a cardiac ablation system for producing a circumferential ablation that electrically isolates a chamber wall portion of a heart from a vessel extending into the wall portion, the system comprising:
(a) an elongate catheter having a distal end portion;
(b) a nonexpandable, compliant, centering element as described above connected to the catheter distal end portion and configured for positioning within the vessel; and
(c) an expandable ablation element connected to the catheter distal end portion, the ablation element configured to form a circumferential ablation on the wall portion around the centering element when the centering element is positioned in the vessel; and
(d) a power supply operably associated with the ablation element.
A sixth aspect of the present invention is a cardiac ablation method for producing a circumferential ablation that electrically isolates a chamber wall portion of a heart from a vessel extending into the wall portion, the method comprising the steps of:
(a) inserting an elongate catheter having a distal end portion through an chamber into the vessel, the distal end portion having a nonexpandable, compliant centering element as described above connected thereto, the centering element having an outer diameter smaller than the inner diameter of the vessel, the distal end portion further having an ablation element connected thereto;
(b) positioning the ablation element on the chamber wall portion; and then
(c) forming a circumferential ablation around the centering element on the wall portion in the chamber and outside of the vessel.